Our interdisciplinary group has developed a pneumatic artificial heart that has FDA approval and is now being used in clinical application as a bridge to cardiac transplantation. Moreover, we have made important strides in the development of an implantable electric artificial heart (seven months survival - world record). We propose continued evaluation of the pneumatic heart in animals (eight - ten animals/yr) with specific attention to device- host interaction including hematologic studies to evaluate blood damage, evidence of platelet activation and thrombosis, exercise physiology during different control modes, the hemodynamic effects of vasoactive and anesthetic drugs to better understand the modes of action of these drugs in artificial heart patients, and the renal physiology to better understand the fluid and salt retention seen in artificial heart animals and patients. Also included in the proposed workscope will be continued clinical application of the pneumatic artificial heart in transplant candidates in shock to provide complete circulatory support prior to transplantation (one to two patients per year). Evidence has accumulated indicating the potential advantages of an artificial heart that requires no percutaneous tubes or wires. Power for such a heart will be provided by a rechargeable portable battery pack, easily carried by the patient. Major progress has been made by our group in developing a compact, reversing brushless DC motor driven heart that uses a roller screw motion translator. We propose to continue the development of this heart. The proposed research includes the use of electrical energy transmission by inductive coupling, eliminating the need for any percutaneous tubes. Electric hearts that take advantage of the most modern mechanical and electrical engineering techniques available will be fabricated in our laboratory. Important modifications will decrease the size and weight of the electric heart and increase the reliability. Bench testing, computer simulation and animal implant studies are important components of the proposed work. Complete development of this system will result in a practical implantable artificial heart that will be a useful therapeutic device for certain patients with end- stage heart disease.